1. Field of the Invention
The present invention relates generally to electrical detection of dicing damage to IC (integrated circuit) chips. More particularly, the subject invention pertains to a method and system for electrical detection of damaged moisture barrier/edge seals on IC chips which include a low-K dielectric material, a moisture barrier/edge seal for the IC chip, and a moisture damage sensor circuit positioned on the IC chip in proximity to the moisture barrier/edge seal.
One or a plurality of moisture barrier/edge seals can be positioned along peripheral edges of the IC chip, and one or more moisture damage sensor circuit(s) can be positioned between the plurality of moisture barrier/edge seal(s), or between an active area of the IC chip and the moisture barrier/edge seal(s), or on a peripheral area of the IC chip outside of the moisture barrier/edge seal(s). The sensor circuit is comprised of a single or a plurality of, via chain(s) including a plurality of vias connected in series, or wire monitor circuit(s) extending in a serpentine conductive path through a plurality of wiring levels and vias, or interconnect(s), and the system can monitor the resistance(s) or leakage(s) or ratio(s) of parameters of the sensor circuit(s).
2. Discussion of the Prior Art
During an IC chip dicing operation, cracks can propagate into the active area of the IC chip, causing fails. Inspections are generally performed after dicing to make sure cracks have not propagated into the chip. Performing an optical microscope inspection on the edges of samples of a chip population is satisfactory for IC chips with conventional SiO2 dielectrics which do not rely on an edge seal.
However, for IC chips with low K dielectrics and moisture barrier/edge seals, this microscopic optical inspection approach can lead to reliability problems because it is expensive to inspect all IC chips, and also such microscopic optical inspections are somewhat subjective in nature.
IC chips with low K dielectrics and metal interconnects which do not form a self-passivating oxide layer, such as copper or silver interconnects, are susceptible to moisture ingress-induced corrosion, and accordingly moisture barrier/edge seals are required to prevent moisture from entering the IC devices. Water can diffuse through low K materials, such as polymers or porous glass, and oxidize the metal wires, causing their resistance to increase or causing leakage between wires due to a volume expansion associated with oxidation of the metal wires. If the moisture barrier/edge seal is damaged, then moisture can enter the IC device during operation, causing failure. Unfortunately, the failure can occur slowly, creating a reliability problem which is difficult to screen for. Therefore, it would be desirable to be able to detect IC chips with damaged moisture barrier/edge seals before they are shipped to customers.
Accordingly, it is a primary object of the present invention to provide for electrical detection of dicing damage to moisture barrier/edge seals of IC chips. The subject invention provides a system and method for detecting moisture penetration into an IC chip having an insulator which includes a low-K dielectric material, a moisture barrier/edge seal for the IC chip, and a moisture damage sensor circuit positioned on the IC chip in proximity to the moisture barrier/edge seal.
In greater detail, a plurality of moisture barrier/edge seals can be positioned along peripheral edges of the IC chip, and the moisture damage sensor circuit can be positioned between the plurality of moisture barrier/edge seals, or positioned between an active area of the IC chip and the plurality of moisture barrier/edge seals, or positioned on a peripheral area of the IC chip outside of the plurality of moisture barrier/edge seals.
A reference sensor circuit can also be positioned on the IC chip, and an electrical parameter such as the resistance or leakage or a ratio of the moisture damage sensor circuit compared to the same electrical parameter of the reference sensor circuit.
The sensor circuit can-comprise a via chain including a plurality of vias connected in series, or a wire monitor circuit extending in a serpentine conductive path through a plurality of wiring levels and vias of the IC chip.
A plurality of sensor circuits can be positioned along peripheral edges of the IC chip to detect when the moisture barrier/edge seal on the IC chip is damaged, and the plurality of sensor circuits can be wired together in series to form a single detection circuit. The plurality of sensor circuits can comprise a plurality of via chains or wiring levels or interconnects, and the system can monitor the resistances, or leakages, or ratios of the plurality of sensor circuits or of two neighboring sensor circuits.